[ticket/11920] Actually call travis/setup-mariadb.sh.

PHPBB3-11920
[ticket/11920] Manually purge mysql-common.

PHPBB3-11920
[ticket/11920] Print MariaDB version after successful setup.

PHPBB3-11920
Merge pull request #1782 from bantu/ticket/11920

[ticket/11920] Actually call travis/setup-mariadb.sh.